Your payload is correct but you need to adjust the encoder it seems, under no circumstances would I advocate using msf, you learn little from that approach and it’s highly discouraged, but I make an exception with boxes whether intentionally or not are dysfunctional. I’m a little ambivalent when I come across a box like it, which is rare, so here’s a riddle, the answer is ‘universally mixed’, and 'W’e 'M’erry 'I’ndividuals can’t just allude to the post local privilege exploit you should use.